1. Field of the Invention
The present disclosure is related to the field of analytical measurements, more specifically it is related to a method for determination of the mobility of inversion charge carriers at the interface surface of a dielectric layer deposited on a semiconductor substrate.
More specifically, it relates to channel mobility measurements of the inversion charges situated at the interface surface of the gate dielectric and the (e.g. silicon) substrate.1.
2. Description of the Related Technology
It is well known that low field mobility of the inversion layer is one of the most important parameters that characterize metal-oxide-semiconductor field-effect transistors (MOSFETs). Attention must be paid that this parameter is well optimized in the gate stack module. However it is not very accessible to be measured, as the electrical characterization in state of the art techniques needs the fabrication of (expensive) transistors to extract it. This is still a hot topic within the CMOS research in trying to understand how different process conditions influence the mobility. Also for the extraction technique, different methods exist and are optimized for particular transistors, e.g. for the ultra thin gate dielectrics that show high leakage [Takagi S-I JJAP Vol 41 p.2348 (2002)].
An existing technique to derive mobility without making transistors is also described by [J. Son et al. Appl. Phys. Lett. 69 (1996) p. 1779]. However an important drawback of this technique is the fact that a polygate structure is needed and the fact that the free carriers are not moving due to an electric field parallel to the interface as it is in transistors.
In order to understand the impact on mobility, it would be good to have information immediately after only the (gate) dielectric deposition, excluding the impact of the metal gate or poly silicon gate (also referred to as gate electrode) which is in a completed gate stack situated above the (gate) dielectric material. On the other hand, for optimization, extended design of experiments (DOE) are necessary to find the ideal process parameters.
For this reason there is a need to extract mobility information from blanket wafers that contain a (gate) dielectric layer.